Copolyimide-isoimide polymers



United States Patent 3,413,267 COPOLYIMIDE-ISOIMIDE POLYMERS John A.Kreuz, Williamsville, N.Y., assignor to E. I. du Pont de Nemours andCompany, Wilmington, Del., a corporation of Delaware No Drawing.Continuation-impart of application Ser. No. 325,441, Nov. 21, 1963. Thisapplication May 17, 1966, Ser. No. 550,647

1 Claim. (Cl. 260-47) This application is a continuation-in-part of mycopending application Ser. No. 325,441, filed Nov. 21, 1963, allowedMar. 2, 1966, and now US. Patent No. 3,271,366.

This invention is related to film-forming copolymers.

More particularly, this invention is directed to the discovery of novelpolyiminolactone/polyimide copolymers of 5-95 mole percent of the formerand-95-5 mole percent of the latter, which copolymers have an unusualand outstanding combination of properties.

The novel copolymers of this invention are characterized by an excellentcombination of properties, including hydrolytie stability, stiffness,toughness, shelfstability, electrical properties, thermochromicity,convertibility to permanently creased or formed articles, flowability,etc. Furthermore, the novel copolymers are characterized by a glasstransition temperature and melt and flow properties rendering thecopolymer particularly useful in the adhesive field, among others.

The copolymers of this invention can 'be prepared in various ways,including those illustrated in the examples below. For example, they canbe prepared by controlled thermal isomerization of polyisoimides, bycatalytic isomerization of polyisoimides with agents such astriethylammonium acetate, and by -treatment of polyamide-acids withconverting agents such as thionyl chloride.

The polyamide-acids, polyisoimides and polyirnides are known and theirpreparation is described for example in a 7 my above-mentioned parentpatent. The polyamide-acids consist essentially of recurring unitshaving the formula:

Let M J.

The polyiosimides consist essentially of recurring units having theformula:

The polyimides consist essentially of recurring units having theformula:

In the above formulas, the arrows denote isomerization; R is an aromatictetravalent organic radical, preferably selected from the groupconsisting of 3,413,267 Patented Nov. 26, 1968 and V wherein R isselected from the group consisting of an I I R4 R5 and ene, and

wherein R is selected from the group consisting of an alkylene chainhaving 1-3 carbon atoms,

wherein R and R are selected from the group consisting of alkyl andaryl; and n is an integer sulficient to provide an inherent viscosity ofat least 0.1, and preferably 0.3-5.0, as measured at 30 C. at aconcentration of 0.5% by weight of the polymer in a suitable solvent,e.g., N,N-dimethylacetamide, concentrated sulfuric acid, etc.

Representative R groups can be conveniently provided, as disclosed in myabove-mentioned parent patent, by aromatic dianhydrides such as:

pyromellitic dianhydride; 2,3,6,7-naphthalene tetracarboxylicdianhydride; 3,3',4,4'-di phenyl tetraearboxylic dianhydride;1,-2,5,6-naphthalene tetracarboxylic dianhydride; 2,2',3,3'-diphenyltetracarboxylic dianhydride; 2,2-bis(3,4-dicarb0xyphenyl)propanedianhydride; bis(3,4-dicarboxyphenyl)sulfone dianhydride;3,4,9,10-perylene tetracarboxylic dianhydride; bis 3,4-dicarboxyph enylether dianhydride; naphthalene-1,2,4,5-tetracarboxylic dianhydride;naphthalene-1,4,5,8-tetracarboxylic dianhydride;2,6-dichloronaphthalene-l,4,5,8-tetracarboxylic dianhydride;

Representative R groups can be conventiently provided,

as disclosed in my above-mentioned parent patent, by H aromatic diaminessuch as:

meta-phenylene diamine; para-phenylene diamine;2,2-bis(4-amino-phenyl)propane; 4,4'-diamino-dipheny-1 methane;4,4'-diamino-diphenyl sulfide; 4,4'-diamino-dipheny1 sulfone;3,3'-diamino-diphenyl sulfone; 4,4'-diamino-diphenyl ether;2,6-diamino-pyridine;

bis-(4-amino-phenyl)diethyl silane;

bis-(4-amino-phenyl) diphenyl silane; benzindine;3,3'-dichloro-benzidine; 3,3'-dimethoxy benzidine;bis-(4-amino-phenyl)ethyl phosphine oxide; -bis(4-amino-phenyl)pheny lphosphine oxide; bis (4-arnino-phenyl) N-butylamine;bis(4-amino-phenyl)-N-methylamine; 1,5-diamino-naphthalene;3,3-dimethyl-4,4'-diaminobiphenyl; N-(3-amino-phenyl)-4-aminobenzamide;4-aminophenyl-3-aminobenzoate; and mixtures thereof.

The invention will be illustrated by the following examples.

EXAMPLE 1 Films of the polyisoimide based on pyromellitic dianhydrideand 4,4-diaminodiphenyl ether were prepared by casting a polyamide-acidsolution (prepared in accordance with Edwards US. Patent No. 3,179,614)with a 2-mil doctor knife onto a polyethylene sheet, drying for 3minutes at 98 C. in a forced draft oven, stripping the polyamide-acidfilms from the polyethylene sheets, placing them in a 1 molar solutionof trifluoroacetic anhydride in benzene for 80 minutes, washing furtherin benzene, and drying overnight under nitrogen under reduced pressure.Analysis of the infrared spectra of these films, in comparison with thespectra of model imides and isoimides, indicated them to be 94% isoimideand 6% imide. The film samples were then clamped into individual framesand places in a forced draft oven at 350 C. for various periods of time,after which they were again examined by infrared analysis. The resultsare given in the following table.

The percentages are thought to be accurate within about i%.

4 EXAMPLE 2 Example 1 was repeated except that l-mil films were castwith a doctor knife, and the resulting films were thermally isomerizedfrom isoimide to imide at 300 C. In this case, the initial film wassubstantially all isoimide. The results of thermal 'isonierization aregiven in the following table, where the analyses are again thought to beaccurate to within about 15%.

Heating time Percent isoimide Percent imide EXAMPLE 3 Films of thepolyamide-acid derived from pyromelletic dianhydride and4,4'-diaminodiphenyl ether, 0.1 to 0.2 mil thick, were prepared inaccordance with Edwards US. Patent No. 3,179,614. They were thensuspended in a one molar solution of thionyl chloride in benzene at roomtemperature for 24 hours, washed in benzene, and dried at roomtemperature under nitrogen at about 15 mm. The infrared spectrumindicated these films to be about 54% isoirnide and 46% imide. Theirphysical strength, 9,000 p.s.i.; and inherent viscosity, 0.26, asmeasured on a 0.1% solution in fuming nitric acid at room temperature.

EXAMPLE 4 To 15.1 grams of a 15% solids solution in N,N-dimethylaceamide of the polyamide-acid based on pyromellitic dianhydrideand cumenediamine (2.3 grams of polymer) (prepared in accordance withEdwards US. Patent No. 3,179,614) was added over 15 minutes 2.78 gramsof dicyclohexylcarbodiimide dissolved in ml. of N,N-dimethylacetamid'e,and the mixture was stirred for 1 hour; it was then cooled, centrifugedto remove the N,N'-dicyclohexylurea by-product, filtered, and cast intofilms with 2-mil doctor knife. The films were dried at room temperatureunder nitrogen at reduced pressure to give polyisoimide films about 0.2mil thick. The resulting films, which were substantially all isoimide,were immersed in a one molar solution of triethylammonium acetate inbenzene at room temperature for minutes, washed in benzene and dried.Infrared analysis of the resulting films indicated them to be 85% imideand 15% isoimide.

EXAMPLE 5 Acetyl chloride (1 ml.) is added at room temperature to 10grams of a 10% by weight solution of the polyamide-acid of pyromelliticdianhydride and 4,4'-diaminodiphenyl ether in N,N-dimethylacetamide.After standing 26 hours the solution is cast into a thin film, which isdried at 50 C. and examined by infrared. The polymer contains about 10%isoimide, 20% normal imide and 70% polyamide-acid.

EXAMPLES 6-9 The procedure of Example 5 is repeated, using instead ofacetyl chloride each of the following cyclizing agents, at 1 molarconcentration in a benezene solution also containing pyridine inequimolar concentration:

6.propionyl fluoride 7.v'aleryl chloride 8.bromoacetyl bromide 9.thiony1chloride The iminolactone content, as measured by infrared spectra, ofeach product is 70 mole percent, the remainder being primarily normalimide.

5 EXAMPLE 10 A deep orange polyiminolactone film is prepared by castinga polyamide-acid film of pyromellitic dianhydiide and4,4'-diamino-diphenyl ether onto a glass plate; drying 1.5 minutes at100 C.; immersing in a 1 molar trifiuoroacetic anhydride solution inbenzene for 1 hour at room temperature; washing in benzene; and thendrying under vacuum.

Samples of the polyiminolactone film are converted topolyiminolactone/polyimide copolymers of compositions varying from 5-95mole percent by immersing the samples in a N,N-dimethylformamidesolution of 0.1 molar triethylammonium acetate. By removing the filmsfrom solution at various times and leaching out the triethylammoniumacetate with fresh solvent, the isomerization is inhibited. Measurementof normal-imide absorbance at 13.85 microns relative to absorbance at10.85 microns shows the extent of isomerization.

The invention claimed is:

1. A linear polymer consisting essentially of 595 mole percent ofrecurring units of the formula where the arrows denote isomerization;

R is an aromatic tetravalent organic radical, preferably selected fromthe group consisting of @mmmn wherein R is selected from the groupconsisting of and wherein R and R are selected from the group consistingof alkyl and aryl;

R is a divalent aromatic radical, preferably selected from the groupconsisting of phenylene, naphthy lene, biphenylene, anthrylene,furylene, benzfurylene, and

wherein R and R are selected from the group consistsisting of alkyl andaryl; i L

I said polymer having an inheren viscosity of at least 0.1 as measuredat 30 C. at a concentration of 0.5% by weight of the polymer inconcentrated sulfuric acid.

References Cited UNITED STATES PATENTS 3,179,630 4/ 1965 Endrey.3,179,631 4/ 1965 Endrey. 3,179,632 4/1965 Hendrix. 3,179,633 4/ 1965Endrey. 3,179,634 4/1965 Edwards. 3,271,366 9/1966 Kreez.

WILLIAM H. SHORT, Primary Examiner.

H. D. ANDERSON, Assistant Examiner.

1. A LINEAR POLYMER CONSISTING ESSENTIALLY OF 5-95 MOLE PERCENT OFRECURRING UNITS OF THE FORMULA